CI: use DejaVu fonts (fonts-charis isn't in Ubuntu apt)

The first run failed because the workflow tried to apt-install
fonts-charis, which is not in the Ubuntu 24.04 repos (it's named
something else in older Debian and was dropped from current).

Swap to DejaVu (fonts-dejavu / fonts-dejavu-core) which is always
available in Ubuntu apt. DejaVu Serif as body, DejaVu Sans for
headings, DejaVu Sans Mono for code blocks. Strip the
Numbers=OldStyle font option in CI since DejaVu Serif doesn't have
oldstyle figures.

Author: DatanoiseTV

.github/workflows/build.yml

@@ -61,18 +61,20 @@ jobs:
       - name: Install fonts
         run: |
           sudo apt-get update -qq
-          sudo apt-get install -y fonts-charis fonts-dejavu fonts-liberation
+          sudo apt-get install -y fonts-dejavu fonts-dejavu-core fonts-liberation
           fc-cache -f
+          fc-list | grep -iE 'dejavu|liberation' | head -5
 
       - name: Swap mac fonts for Linux substitutes
         # GitHub runners don't have macOS Charter / Helvetica / Menlo.
-        # Use widely-available substitutes during CI builds only;
-        # the committed metadata.yaml stays mac-friendly.
+        # Substitute with DejaVu (ships with fonts-dejavu, always
+        # available); the committed metadata.yaml stays mac-friendly.
         run: |
           sed -i \
-            -e 's/^mainfont:.*/mainfont: "Charis SIL"/' \
+            -e 's/^mainfont:.*/mainfont: "DejaVu Serif"/' \
             -e 's/^sansfont:.*/sansfont: "DejaVu Sans"/' \
             -e 's/^monofont:.*/monofont: "DejaVu Sans Mono"/' \
+            -e '/^mainfontoptions:/,/^[^ ]/{/Numbers=OldStyle/d}' \
             metadata.yaml
           grep -E '^(mainfont|sansfont|monofont):' metadata.yaml